Preparation Of Multi-functional Supported Rubber Vulcanizing Agents On Their Effects On The Structure And Properties Of Rubber Composites

With the continuous development of the rubber industry and the enhanced awareness of environmental protection,to prepare novel,high-performance,multi-functional,low cost and “green” rubber additives have gradually become a new direction for the development of rubber industry.Rubber vulcanization is a key factor to meet the performance of rubber materials.Since the development of rubber industry from the nineteenth century,sulfur is the most used vulcanizing agent.However,the traditional sulfur vulcanization system with the problems of poor solubility,uneven crosslinking structure,high free sulfur content and reversion,which impact the performance of vulcanized rubber.Sulfur vulcanization reaction is often characterized by the polysulfide bond with poor thermal stability.With the increasing of curing time,the polysulfide bond will cause the reversion phenomenon which resulting in poor mechanical properties of vulcanized rubber.On the other hand,filler is one of the key factors to determine the ultimate performance of rubber materials.Therefore,this paper combines the problem of rubber vulcanization and filler modification to prepare novel and multi-functional filler supported rubber vulcanizing agents,and their influence on the structure and properties of the rubber/inorganic filler composites.It is a subject with significant innovation,important theoretical and practical meaning.Based on the development of "green tire" industry with low rolling resistance,high wet resistance and high wear resistance,and combined two important problem of the preparation of novel multi-functional rubber vulcanizing agents and the surface modification of nano-filler,four kinds of novel and multi-functional filler supported rubber vulcanizing agents were prepared: silica-s-S₂Cl₂,HNTs-s-S₂Cl₂,silica-s-VA7,and silica-s-DCBPO.Meanwhile,their vulcanization properties,dispersion in rubber matrix,the effect on the structure and properties of rubber composites by the enhanced filler-rubber interfacial interaction had been investigated systematically.?1?Three kinds of silica supported rubber vulcanizing agent?silica-s-S₂Cl₂?in different sulfur content?13.13%,21.26% and 36.84%,respectively?were prepared by the chemical reaction between high activity compound S₂Cl₂ and hydroxyl groups on the silica surface.The structure,composition and the sulfur loading content of the supported vulcanizing agent were studied.Meanwhile,the properties of the vulcanized rubber cured by sulfur and silica-s-S₂Cl₂ respectively were compared.Compared with sulfur vulcanization system,the supported vulcanizing agents with lower free sulfur content were harder to migrate and volatilize than that of sulfur.SBR/silica-s-S₂Cl₂ composites with higher crosslinking density were give priority to the mono-and disulfides crosslinking.To the contrary,SBR/sulfur composite was based on polysulfide crosslinking.The novel supported vulcanizing agent silica-s-S₂Cl₂ could not only crosslink the rubber chains,but also improve the filler dispersion in the rubber matrix.The quantitative analysis proved that the content of immobilized rubber layer on the filler surface had significantly increased,and markedly enhancing the interfacial adhesion in the composites which cured by silica-s-S₂Cl₂.The study on the dynamic mechanical property of SBR composites shown that with the increasing content of silica-s-S₂Cl₂,the rolling resistance decrease.On the other hand,silica-s-S₂Cl₂ as a vulcanizing agent could effectively improve the thermal oxidation aging property of composites.?2?The optimum sulfur loading content of silica-s-S₂Cl₂ was applied to natural rubber to compare with sulfur on the performance.It was found that the vulcanization system of accelerator CZ and silica-s-S₂Cl₂ had the best effect on the vulcanization and acceleration.As the content of silica-s-S₂Cl₂ increasing in NR matrix,the filler dispersion was improved.Moreover,the content of immobilized rubber layer and the crosslinking density of the composites were also significantly increased.Compared with the NR/sulfur composite,the tensile strength,modulus at 100%,modulus at 300% and the tear strength of NR/silica-s-S₂Cl₂-10 composite was increased by 23.4%,14.3%,10.8% and 11.2% respectively.The study on the dynamic mechanical property of NR composites shown that the tan? values at 60 ? drastically decreased with the increasing content of silica-s-S₂Cl₂.Comparing with the NR/sulfur composite,the tan? values at 60 ? of NR/silica-s-S₂Cl₂-20,NR/silica-s-S₂Cl₂-15 and NR/silica-s-S₂Cl₂-10 composites are decreased by 40.9%,34.2% and 15.1% respectively,which shown the significantly reducing of the rolling resistance for NR/silica-s-S₂Cl₂ composites.?3?Another kind of supported vulcanizing agent,HNTs-s-S₂Cl₂,was prepared by the chemical reaction between S₂Cl₂ and hydroxyl groups on the surface of HNTs.The properties of the vulcanized rubber cured by sulfur and HNTs-s-S₂Cl₂ respectively were compared.The sulfur loading content,the surface structure and composition of HNTs-s-S₂Cl₂ were characterized.It was found that with the increasing content of HNTs-s-S₂Cl₂ in NR matrix,the filler dispersion was improved obviously and the tubular filler showed excellent orientation.Meanwhile,the content of immobilized rubber layer and the crosslinking density of the composites were also significantly increased.The investigation on the dynamic mechanical property of NR composites shown that the values of the tan? at 0? were increased with the increase content of HNTs-s-S₂Cl₂,to the contrary,the values of tan? at 60? were drastically decreased.It means that the NR/silica-s-S₂Cl₂ composites exhibit excellent properties of low rolling resistance and high wet resistance.?4?Supported vulcanizing agent silica-s-VA7 was prepared by using silica as carrier and aliphatic ether polysulfide?VA-7?as loading.The mechanical properties,crosslink density,filler network structure and thermal aging performance of SBR/silica-s-VA7 and SBR/sulfur vulcanized systems were compared.The results shown that the supported vulcanizing agent silica-s-VA7 could effectively improve the filler dispersion in SBR matrix,and its vulcanized system had more excellent mechanical property and thermo-oxidative aging property than that of sulfur vulcanized system.?5?The surface of the silica was modified by the silane coupling agent ?-aminopropyltriethoxysilane?KH550?firstly,and then reacted with 2,4-dichlorobenzoyl peroxide?DCBPO?to prepare supported vulcanizing agent silica-s-DCBPO for silicone rubber?SR?vulcanizing.The filler network structure,the filler dispersion,the mechanical properties and crosslinking density of SR/silica-s-DCBPO and SR/DCBPO vulcanization systems were compared.It was found that the supported vulcanizing agent silica-s-DCBPO could effectively improve the dispersion of the filler in SR matrix and the filler-rubber interfacial interaction.With adding 6 phr silica-s-DCBPO into the matrix,the SR/silica-s-DCBPO composite achieved the best performance.